1. Field of the Invention
The present invention relates to a method for accurately positioning a magnetic head on a destination track of a magnetic disk and a magnetic disk driving apparatus for implementing the method.
2. Description of the Related Art
In order to position a magnetic head on a destination track of a magnetic disk in a conventional magnetic disk device, the magnetic disk has been used on which, for example, a servo pattern is recorded. The servo pattern is comprised of, for example, two patterns, each of which exists at one side with respect to a track center. Two signals are read from the two patterns. When the magnetic head is positioned off from the center of a desired track, the signals read from the two patterns are such that the signal corresponding to one of the patterns has a peak value larger than the signal corresponding to the other pattern. On the other hand, when the head is positioned right over the center of the desired track, the signals corresponding to the patterns have an equal peak value. Thus, by moving the magnetic head until the signal corresponding to one of the patterns and the signal corresponding to the other of the patterns have equal peak values, the magnetic head can be positioned right over the center of a desired track.
A known method for improving the positional accuracy of the magnetic head is one in which peak values obtained for each of the patterns are averaged for subsequent comparison. This method permits accurate measurement of the amount of positional deviation of the magnetic head from a given track center. On the other hand, if error signals arise due to the disturbance and disk deficiencies at the servo pattern portions, the signals read from the patterns and hence the average values could have abnormal values. This would move the magnetic head to an erroneous position.